Juan R. Pardo-Carrion
Main Results

Broadband Submillimeter Measurements of the Full Moon Center Brightness Temperature and Application to a Lunar Eclipse


Observations of the Full Moon brightness temperature covering the frequency range of 300-950 GHz are necessary as the object is a primary calibrator for our Fourier Transfrom Spectroscopy work on the giant planets at the Caltech Submillimeter Observatory. In order to obtain the correct values of the Moon brightness temperatures at all frequencies we carefully corrected for the atmospheric absorption, which varies across the submillimeter domain. This correction is fully described in this paper. In order to achieve better accuracy in this correction, the FTS observations are supplemented by measurements of the atmospheric opacity using a 183 GHz Water Vapor Monitor.

For this work, the telescope was pointed to the center of the lunar disk, with a beam size of ~ 45 to 15 km on the Moon at 300 and 900 GHz respectively.

On July16, 2000 we were even able to follow a lunar eclipse though only covering the frequency range 165-365 GHz due to poor atmospheric transmission at higher frequencies. The measured pre-eclipse brightness temperature is around 337 K in the 165-365 GHz range. This temperature slightly increases with frequency to reach ~353 K at 950 GHz, according to previous broader band data. The magnitude of the temperature drop observed during the eclipse at 265 GHz (central frequency of the band covered) was about ~ 70 K, in very good agreement with previous millimeter-wave measurements of other lunar eclipses. We detected, in addition, a clear frequency trend in the temperature drop that has been compared to a thermal and microwave emission model of the lunar regolith, with the result of a good match of the relative flux drop at different frequencies between model and measurements.

You can get more information about this work by downloading paper 43 from my publications list.

Upper Panel: Raw antenna temperature measured by the FTS towards the center of the Full Moon, for three different airmasses and without atmospheric correction.

Middle Panel: Antenna temperature after atmospheric correction (see paper 43).

Lower Panel: Fully reduced Equivalent Blackbody Temperature of the Full Moon Center.






The lunar eclipse of July 16, 2000.



Evolution of the Equivalent Blackbody Temperature of the Full Moon Center during the Lunar Eclipse of July 16, 2000 compared to a thermal model of the Lunar Regolith. See details in paper 43.